Prolactin (Prl) is an important osmoregulatory hormone in lower vertebrates. It has frequently been proposed that Prl might serve a similar function in mammals. In man, significant water and salt retention has been reported after injection of ovine Prl, and Prl secretion has been claimed to be under osmoregulatory control. In sheep, the administration of exogenous ovine prolactin restores sodium retention during mineralocorticoid escape. This study was designed to examine the effects of endogenous Prl stimulation on renal water and electrolyte handling under metabolic balance conditions in man. 5 normal volunteers (3 male, 2 female) were placed on a 100 mEq Na, 100 mEq K, 2000 ml water, isocaloric diet. Weight, blood pressure, urinary volume, creatinine, Na, K, osmolality, 17 hydroxy-, 17 ketosteroid and aldosterone excretion were measured daily. After metabolic balance was achieved, 9 α fluorocortisol 0.2 mg/day was added to the regimen, and the subjects were allowed to escape from mineralocorticoid action. During the escape phase, their response to 3 bolus injections of TRH (100-400 μg) every other day was observed. TRH resulted in a 2-4 hour elevation of Prl from baseline to peak values of 72-428 ng/ml. No significant difference in any of the urinary parameters measured was found between control days and periods of Prl stimulation, either during the 2-4 hours of acute Prl elevation or as a cumulative effect over the 7 days of repeated stimulation. It is concluded that in contrast to the sheep, in man endogenous Prl at physiological concentrations does not appear to be an important regulating factor of water and electrolyte excretion in escape, at least during short term stimulation.
|Original language||English (US)|
|State||Published - Jan 1 1975|
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